Those planning to purchase health insurance on the Obamacare exchange will soon find out how much rates have increased — after the Nov. 4 election.

Enrollment on the Healthcare.gov website begins Nov. 15, or 11 days after the midterm vote, and critics who worry about rising premium hikes in 2015 say that’s no coincidence. Last year’s inaugural enrollment period on the health-care exchange began Oct. 1.

“This is more than just a glitch,” said Tim Phillips, president of free-market Americans for Prosperity, in a Friday statement. “The administration’s decision to withhold the costs of this law until after Election Day is just more proof that Obamacare is a bad deal for Americans.”

Robert Laszewski, president of Health Policy and Strategy Associates, said in a Monday column in USA Today that “when it comes to a lack of openness and transparency about Obamacare, this administration has no peer.”

Even so, details about cost increases are trickling out in states with pivotal Senate contests: Alaska, Iowa and Louisiana. All three states are wrestling with double-digit premium hikes from some state insurance companies on the exchange, which has fueled another round of Republican attacks on the Affordable Care Act.

It’s the Democrats’ bad luck that those states may be outliers. PriceWaterhouseCoopers’ Health Research Institute reports Oct. 3 that the average premium increase this year is 5.9 percent, according to data collected from 40 states and the District of Columbia.

The most dramatic increases are underway in Alaska, where the state insurance division has cleared double-digit rate hikes for two insurers, Premera Blue Cross and Moda Health. Premera’s premiums will rise by 35 to 40 percent, although 88 percent of Alaskans on the exchange won’t feel the full effects because they qualify for federal subsidies, according to the Alaska Dispatch News.

“Did you lose your coverage due to ObamaCare? Are your premiums set to skyrocket? Follow the link to share your ObamaCare story and stand up to the elected leaders in D.C. who sold Alaskans out,” said Mr. Sullivan in the Sept. 12 post.

The Iowa insurance commissioner approved last week premium increases for three insurance carriers: Wellmark Blue Cross and Blue Shield, CoOpportunity Health and Coventry Health. Two of those insurers will implement double-digit hikes ranging from 11.9 to 19 percent, the Des Moines Register reports.

“Today’s report that Obamacare is leading to increased premiums in Iowa is bad news for the thousands of Iowans who will now have higher health care costs—some will see out-of-pocket costs rise by as much as 19 percent,” Ms. Ernst said in a Thursday statement.

The issue is also resonating in the Louisiana Senate race, where Democratic Sen. Mary Landrieu is seeking re-election against Republican Rep. Bill Cassidy. Documents filed with the Louisiana Department of Insurance show some insurers are anticipating double-digit rate hikes, according to the New Orleans Times-Picayune.

Mr. Cassidy, who’s a doctor, issued a statement Thursday calling the higher premiums “another hurdle for families and businesses already struggling under the demands of Obamacare.”

“Premiums have gone up by 53 percent for the average Louisiana policyholder and many of these policies will again see double-digit increases,” Mr. Cassidy said. “It’s unfair to Louisianans who have to balance their budgets and their businesses.”

Some analysts say that the Obamacare issue is losing steam, but that may come as news to Republicans. Dozens of GOP candidates released statements decrying Obamacare on Oct. 1, the one-year anniversary of the rollout.

Mr. Cassidy released a video Sept. 29 featuring three Louisiana voters who say they previously backed Ms. Landrieu but now they’re supporting him as a result of her vote for the Affordable Care Act.

“Sen. Landrieu, I voted for you before, but when you voted for Obamacare, I knew I’d made a mistake,” says a woman named Rose in the video.

This year’s enrollment period is also half as long as last year’s six-month window. The launch starts Nov. 15 and ends Feb. 15 for coverage beginning Jan. 1.